Foot areas, ground reaction forces and pressures beneath the feet of kangaroos, wallabies and rat-kangaroos (Marsupialia: Macropodoidea)

Abstract

Foot areas of a wide range of kangaroos, wallabies and rat-kangaroos were measured from fresh material and museum specimens. The areas of the plantar pads scaled according to the predictions of geometric similarity. The terminal claw areas of digits IV and V scaled with a lower than predicted exponent, reflecting functional demands of different species. The pressure that these marsupials exert on the ground during quiet standing is proportional to (body weight)^0.35, and is considerably lower than those exerted by ungulates. Hopping kangaroos exert pressures proportional to (body weight)^0.37. The pressures exerted by medium and large macropods are comparable to those of galloping ungulates. The findings support the commonly held belief that introduced grazing animals may cause greater mechanical disruption of the soil surface, leading to increased rates of soil erosion, than Australia's indigenous grazing fauna.